This invention relates generally to a lock for a rotatable member the base of which is generally stationary and the rotational portion of which is disposed to be angularly moved through a relatively small angular range. This invention relates specifically to a locking device for the shaft of a panel mounted potentiometer including the dial knob and the like.
Axially adjustable locking members have been utilized with a flange on a rotating shaft to stop or prevent rotational movement of that shaft. One example of this is an automotive disk break. A disk breaking system is utilized to generally gradually provide a friction force to a rotating flange to cause the rotating flange to slow. In the field of electronics, panel mounted potentiometers and the like are provided with locking mechanisms. One type comprises a locking nut which is threaded around the shaft of a potentiometer. A screw driver is used to angularly adjust the position of the dial. With the potentiometer in the fixed angular position, the nut is turned with a wrench against the potentiometer base in such a manner as to provide radial pressure against the shaft to prevent further movement thereof. Since a nut is utilized, a wrench or similar means must be available for turning the nut into the locking position. In addition, since the nut is turned angularly and circumferentially around the shaft of the dial, there is always a possibility of causing the shaft to inadvertently rotate through a small angular increment during the locking operation which of course is undesirable. In another kind of locking mechanism, a calibrated dial is provided which fits over the shaft of the potentiometer. The calibrated dial may be turned through a number of revolutions until a desirable angular position is reached in which case a small lever which is disposed on the casing of the calibrated dial may be circumferentially moved to lock the position of the dial. The small angular displacement of the lever may cause inadvertent bumping or touching of the dial during the locking operation or may cause slight movement of the shaft as the locking operation is completed. It would be advantageous to provide a potentiometer or similar rotational electronic device which has a turnable dial or handle which can be conveniently locked in a fixed angular position with minimal disturbance to the setting of the dial such as where the locking operation is predominantly axial to the potentiometer shaft rather than circumferential or radial to it. It would also be advantageous if this operation would not cause significant axial movement of the potentiometer during the locking operation which might cause the potentiometer to be torn away or loosened from the circuit support means upon which it is mounted or disposed.